Sign language provides a means to understand the sensory-motor influences on the neural organization of language. The goals of the present proposal are to uncover the neural basis of sign language using modern lesion-deficit mapping. This will not only answer some fundamental questions about the neural basis of sign language and related processes and address questions about the sensory-motor forces that shape language organization generally, but will also provide much needed information on the clinical-anatomic correlates of sign language aphasia. We propose three specific aims. Aim 1: To determine whether the overall lesion pattern associated with sign language aphasia is similar to that found for spoken language using quantitative lesion-symptom mapping methods. Aim 2: To map the lesion pattern associated with more fine-grained measures of sign language production, sign language comprehension, and related function using quantitative lesion-symptom mapping methods. Aim 3: To assess the neural basis of naming ability and working memory for signs using the lesion method. PUBLIC HEALTH RELEVANCE: An important aspect of the mission of NIDCD is research that leads to increased understanding and treatment of language and communication disorders, particularly with respect to deafness and sign language. Relatively little research has targeted the breakdown of sign language as a result of brain lesions until our previous studies;the program proposed here using modern lesion-symptom approaches provides important new tools for the understanding and treatment of language disorders in deaf signers. This will have implications across a wide range of public health domains and directly benefits clinicians, educators, and individuals caring for deaf signers with brain lesions and/or language disorders.